Comments on: mtDNA, selection and paleoanthropology

By: razib

razib — Tue, 20 Sep 2005 14:47:47 +0000

I've got it all confused.

it isn't you who's confused, it is the field. but david's narrative hits close to the mark on one of the main ideas out there.

By: Darth Quixote

Darth Quixote — Tue, 20 Sep 2005 13:37:47 +0000

No, I wasn’t joking. I’m pretty ignorant with regard to the human diaspora. I think I recognize the scheme that you describe from Cavalli-Sforza’s Genes, Languages, and Peoples, but I’m not sure. In any case my recent skimmings of papers by Harpending and colleagues had led me to believe that there were two distinct waves of settlement, one into Eurasia and another toward Southeast Asia and Australia. But maybe I misread them and I’ve got it all confused.

By: David Boxenhorn

David Boxenhorn — Tue, 20 Sep 2005 11:46:03 +0000

Darth: Is that a joke? In case you’re serious, the basic scheme, as I understand it: Arabia was the first stop out of Africa, followed by settlement of the southern part of Asia (i.e. South and South-East Asia), reaching Australia 40,000-60,000 years ago. Only later did settlement move north.

By: Darth Quixote

Darth Quixote — Tue, 20 Sep 2005 11:24:19 +0000

I'm a little confused, David. Do you mean Eurasia was settled by modern humans from Arabia, South Asia, Southeast Asia, and Australia?

By: David Boxenhorn

David Boxenhorn — Tue, 20 Sep 2005 11:08:56 +0000

Coming back after a day, I’m skeptical that the difference between African and Eurasian mtDNA lineages is due to cold-adaption. The original settlement of Eurasia from Arabia, across South Asia, to South-East Asia and Australia is also very warm territory. Any cold-adaption came much later.

By: Rob

Rob — Tue, 20 Sep 2005 08:36:27 +0000

I'd be interested to see if there are any clear and consistent data from biracial children. Do the children of black fathers and white mothers live longer, play sports better, etc than if the sexes of the parents are switched

or if we can get results consistent with the mtDNA selection hypothesis from breeding cold and warm weather adapted members of the same species.

The hypothesis also makes it more clear why maternal mtDNA is inherited: Paternal DNA is crazy selected for making fast sperm.

By: Darth Quixote

Darth Quixote — Mon, 19 Sep 2005 11:43:16 +0000

It just occurred to me that most African Americans should have the mtDNA variants brought over by the slaves. After all, most of the white admixture in the black populations surely comes from white males. It follows that African Americans are running for the most part on ancestral African mitochondria.

By: Darth Quixote

Darth Quixote — Mon, 19 Sep 2005 11:18:26 +0000

Very interesting indeed.

Wouldn’t it be easy to genotype athletes in the more explosive sports (track, basketball, etc.) to see if certain mtDNA variants are more frequent? White athletes might be most informative.

By: David Boxenhorn

David Boxenhorn — Mon, 19 Sep 2005 10:23:17 +0000

Take a look at his follow-up too.

However, I am puzzled by his puzzlement:

And while I'm at it, why should it be that low-latitude populations have high-ATP-producing variants? As far as I can tell, it's a total mystery that isn't addressed in the least.

Am I missing something? Isn't it obvious that you normally want respiration to be maximally efficient? It's only in cold climates that you have an additional need for heat production.

By: David Boxenhorn

David Boxenhorn — Sun, 18 Sep 2005 23:37:46 +0000

That was very interesting!

Can’t we now correct for selection in calculating time-depth by looking at the ratio of neutral to non-neutral substitutions?